1. Technical Field
The present invention relates to reducing speckle noise generated in a laser display device, more specifically to a diffuser that reduces the speckle noise by actively changing the shape of scattering pattern of the diffuser having various shapes of scattering pattern and a laser display device having the diffuser.
2. Background Art
With the rapid growth in display technologies, display devices using laser as light source have been developed. The laser light source has better intensity and luminance than other light sources and thus can provide a clear image with a high contrast and can be realized in a small device. However, due to the high coherence, the laser light source generates speckles, which become a problem in the display. A speckle, which is a spot pattern that is generated by peculiar wave properties of an incident laser ray according to the surface roughness of a screen, deteriorates the screen quality significantly. Accordingly, there have been a variety of methods to reduce the speckle.
In one of the conventional technologies, a diffuser is provided to the display device and is made to move in order to reduce the speckle. Specifically, a laser ray is penetrated to the diffuser that is rotating or vibrating. As the diffuser rotates, the degree of penetrated and diffused laser ray is made irregular, or the phase of the laser ray is made irregular. Accordingly, the coherence, which is the peculiar characteristic of a laser ray, is reduced.
In another method, a wave front modulator is provided to a display device to reduce the speckle. By penetrating the laser ray through the wave front modulator, the phase of the laser ray is changed. The wave front having a phase spatial change generates multiple speckle patterns to reduce the speckle. In yet another method, the display screen is moved or vibrated.
However, since the above-described conventional methods use the rotation or vibration of the diffuser or screen to reduce the speckle, the display device or screen becomes to jiggle, causing displeasure to the viewers and making the display device unstable.